Endoscopes are used in a variety of medical procedures to see inside the body. Rather than make a large incision and expose the surgical site to view, various types of endoscopes are used which are designed to be inserted into the body through a natural orifice or through a substantially smaller puncture or incision. Many forms of endoscopes are known in the art. They generally comprise an elongated multiple lumen tube having a proximal end and a distal end. Included among the plural lumens is one containing an optical fiber or bundle of such fibers for transmitting light from a light source coupled to the proximal end of the tube to the distal tip for illuminating the vessel or organ cavity to be examined. Another lumen is typically used to contain a further optical fiber for transmitting the illuminated image to an eye piece or other viewing device coupled to the proximal end of the endoscope. An endoscope will further typically include a lumen comprising a working channel through which flushing liquid may be injected and aspirated. The working channel may also provide a pathway through which other instruments may be passed through to the location where the treatment is to be affected.
Rigid endoscopes, without tools or working channels, can be used strictly to monitor a surgical procedure. Typical of such devices are laparoscopes, such as is used during laparoscopic cholecystectomy procedures. The laparoscope is inserted through a small puncture wound in the abdominal wall and various other cannulae or tubes are likewise inserted allowing cutting or grasping instruments to be introduced through the lumen of these cannulae. The surgical field is observed on a display device (TV monitor) coupled to the laparoscope. The optical system employed in the rigid endoscopes does not allow the endoscope to be bent and this necessarily limits the ability of surgeon to gain access to many areas of the body to be worked on.
A flexible deflectable endoscope, on the other hand, provides access to areas of the body that are only accessible through tortuous, curved passages. Incorporating a working channel in a flexible deflectable endoscope allows the surgeon to pass a flexible tool through the channel to manipulate tissue at the distal end of the endoscope.
There are two types of flexible deflectable endoscopes. One type is passively deflectable, being bent by curved passages or other tissue. The other type is actively deflectable. Actively deflectable endoscopes are mechanically activated by the physician. The physician deflects the endoscope by means of one or more pull wires located inside the endoscope tube. These pull wires are anchored near the distal tip of the tube and they are free to move within the endoscope for the remainder of its length. The proximal end of the endoscope tube is held securely in a hand piece. When the wires at the proximal end are pulled such as by actuating a thumb slide member, the distal tip of the endoscope deflects. The further the wire is tensioned, the more the distal tip deflects. As endoscopes have become smaller, structural strength limits are more easily reached, making a force limiting feature desirable. The problem created by the smaller endoscope is that the user may exert excessive force on the endoscope tip during deflection. Tissue can be damaged if this excessive force occurs when the endoscope tip is bound by body tissue. The user can also damage the endoscope if excessive force is exerted on the endoscope tip during deflection if the endoscope tip is within a rigid cannula.
To overcome these potential problems, the present invention adds a force limiting coupler such as an elastomeric band or a tension spring to the proximal end of the deflection wire where it joins to the thumb slide actuator. The invention also includes a backstop to limit the amount of travel of the deflection wire. As the thumb slide is pulled back toward the proximal end of the hand piece, it pulls on the force limiting coupler, which in turn pulls on the deflection wire. The addition of the force limiting coupler allows the user to deflect the distal end of the endoscope in finer increments and acts to preclude potentially damaging forces to be applied to the endoscope or to tissue.